Heat exchange apparatus



Max:119 194s; J.E.WOODS 2,431,281

HEAT EXCHANGE APPARATUS Filed Dem- 15, 1943 Patented Mar. 9, 1948 v IHEAT EXCHANGE APPARATUS John E. Woods, Brooklinc, Mass., assignor, bymesne assignments, to Standard-Thomson Corporation, Boston, Mass, acorporation of Delaware Application December 15, 1943, Serial No.514,383

2 Claims. (Cl. 257-2) 'apparatus of the thin The present inventionrelates to heat exchange apparatus and thermostatic control devicestherefor, and is more particularly concerned with control devices forradiators, oil coolers, and other heat exchange apparatus or the typessuitable ior use in aircraft.

Oil coolers and similar heat exchange apparatus for aircraft are usuallymounted in ducts extending through the wing. The heat exoperating range.As applied to heat exchange tube type, the control members are in theform 01' tips applied to the individual tubes.

Other features of the invention consist of certain novel features ofconstruction and combinations oi parts hereinafter described. in thespeciflcation and particularly claimed in the claims.

In the accompanying drawings, Fig. 1 is a section through a portion 01'a heat exchanger changer has channels for. flow of the fluid to be 1illustrating the application of individual concooled and channels forflow of cooling liquid, trol devices according to the present invention.the two sets 01' channels being in heat exchange the control devicesbeing shown in closed posirelation.- In one widely used. form oiunit,.the tion; Fig. 2 is an end view of oneof the conchannels for the,flow oi cooling fluid will com-- trol devices; Fig. 3 is a sectionalview of the rear prise thin-wall, closely spaced tubes, whilethe part ofthe heat exchanger shown in Fig. l; but channels for the flow of fluidto be cooled comwith the control devices open; Fig. 4 is a view prisethe external inter-tube spaces. illustrating the manufacture of thecontrol mem- In connection with heat exchange apparat bers; Fig. 5 isvan end view of one of the control for aircraft, shutters are fr quentlyprovid d to devices in open position; and Fig. 6 is a sectional diminishthe flow of air through the cooling chanelevation of a modifiedarrangement. nels at low temperatures. In oil coolers espec- Fig. 1illustrates a heat exchanger of the genially, vproper'control under coldconditions preeral type described in my Patent No. 2,298,996, sents aserious problem, since at high altitudes comprising closely spacedthin-wall tubes 4, 1 under low power conditions, the oil congealsmounted at opposite ends in a rear header plate in the inter-tube spaces01' the cooler. In order 6 and a front header plate 8. As an example,one to free the oil, special warm-jackets with therconstruction employstubes .210" in diameter mostatically controlled valves are provided inthe and about .006" in wall thickness, spaced about oil circulatingsystem. It is also important to I .260" on centers. Some units have 3000or more shut oil! or at least diminish the flow of cooling tubes. At thefront-ends the tubes may be exfluid through the tubes until thetemperature 80 panded,.as indicated 'at l0 and as described in rises tothe normal operating range. my patent. The tubes project slightlythrough The use of shutters for controlling the flow the rear header, asindicated at I l, The tubes 01' air is attended with a number 01difficulties. are suitably secured to the headers by soldering, Theshutters are ordinarily operated manually, by brazing as described in mypatent, or in any and therefore do not respond accurately to tem- 5other suitable manner. perature conditions within the unit. For con.- Asis customary in devices .of this kind,the enstructional reasons, theyare usually placed at tire unit is enclosed in a tank or casing havingthe end of the duct where the air, emerging from suitable inlet andoutlet ports for introducing the duct, enters the air stream. Hence, anytheoil into the spaces between the tubes 4. The changes in shutterposition are likely to intro- 40 unit is placed in the cooling duct orthe plane duce aerodynamic disturbances which affect the in such adirection that the air flows through drag on the airplane. Furthermore,congealed the tubes in the direction 01' the arrow. In the oil in thecooler thaws out progressively from end of each'tube isprovideda,control member one point to another, and hence the flow of air in theform of a tip, indicated generally at I 4. should be controlledindependently through dii- Each tip is formed from bendable thermostaticferent sections 01 the cooler, an operation which I, material such asbimetal. The tips are preferis impossible with the conventional shutter.ably formed by stamping them out of a sheet or According to the presentinvention, the coolbimetal, as illustrated in Fig. 3, each member ingfluid channels are provided at the'rear of the having a tab l8 sothatfthe member may be unit with individual temperature controlledclorolled up, with a cylindrical base portion, and sure devices. Thesedevices operate to close the soldered or welded by the overlapping tabit. As cooling fluid channels when the temperature of shown in Fig. 3,the member H in flatform is the air is below the normal operating rangeand provided with a series of petals I8 of such shape to open them asthe temperature approaches the that the petals are in close contact inthe completed tip when the metal is at low temperatures.

At higher temperatures the metal bends and the petals open outwardly asshown in Fig. 3. The tips are slipped over the protruding ends l2 of thetubes and are secured in position by soldering, or by means of anadhesive lacquer.

At low temperatures, the control members are closed, as shown in Figs. 1and 2, substantially blocking the air flow through the tubes except forinconsequential leakage between the petals l8. In an oil cooler, thisrepresents the condition in which the oil is at low temperature, so thatthe air in the tubes 4 is not heated. As th oil thaws out and andincreases in temperature, the air is warmed in its passage through thetubes 4 and the warm air passing over the petals l8 causes them to bendoutwardly, thereby opening the passage. The amount of opening of thepetals is determined by the air temperature. The thermostatcharacteristics are determined by the fact that the control membersshould be fully open as indicated by Fig. 3 for normal operatingtemperatures.

It will be observed that the controls are applied to the individualtubes whereby the control members operate in response to the air flowthrough their respective tubes. Since the oil necessarily warms up atdifferent rates in the different sections of the cooler, the airtemperatures are proper for the different conditions existing indifferent parts of the unit.

Attention is directed to one important feature of the device. It will beobserved from Fig. 3 that if the petals open more than indicated, thepetals of adjacent tubes will engage one another and thus limit theextent of opening movement. Except for this feature, the petals of onecontrol member might, under overheating conditions, expand sufficientlyto block the passage of air through an adjacent tube or tubes. Accordingto this invention, the tubes are fully open for normal operatingtemperatures and all higher temperatures.

In the arrangement shown in Fig. 6, a thermostatic member 20 is placedinternally of each tube, preferably at about the middle of the tube.This arrangement is important from aerodynamic considerations.

The cooling air upon engaging the front ends of the tubes has someturbulence imparted to it. This turbulence, although it increases thepressure drop, is advantageous in enhancing the heat transfer. In thecase of the plain tube unit, as the air progresses along the tube, theturbulence tends to damp out, so that at some intermediate point, theflow becomes laminar, or nearly so. The laminar flow in the remainingtravel through the tube contributes little to the heat exchange.

According to the construction in Fig. 6, the thermostatic member 20 inan intermediate portion of the tube obstructs the flow slightly, evenwhen wide open, and thus introduces some turbulence. The turbulence thusintroduced improves the heat transfer, although with some unavoidableincrease in pressure drop.

It will be understood that the requirements of high heat transfer andlow pressure drop are inconsistent and that an improvement in heattransfer is usually accompanied by an increased pressure drop. However,according to the present invention the obstruction of the passage by useof the inserted members is a minimum because the petals, when open,conform to the inside walls of the tube. Hence the turbulence is no morethan necessary to prevent the occurrence of laminar flow from the placeoccupied by the control member to the rear of the tube.

In manufacture, each control member has its base portion coated withadhesive lacquer and is inserted a definite distance into the tube. Thepetals open and close under temperature changes as in the constructionpreviously described.

Although the invention has been illustrated and described as embodied ina header-type heat exchanger using thin-wall tubes, it will beunderstood that the invention is not limited to this construction but isapplicable to the use of bendable thermostatic leaf members arranged atthe rear of individual cooling fluid channels of other types of units.

Having thus described my invention, I claim:

1. In an aircraft oil cooler having tubes for the flow of cooling fluidtherethrough, control devices applied to individual tubes at the rearthereof and having bendable thermostatic leaves operating to close thechannels at low temperatures and to open for substantially unrestrictedflow at normal and higher temperatures, adjacent control devices openingoutwardly to engage one another to limit the extent of movement atexcessive temperatures.

, 2. In an aircraft oil cooler having tubes for flow of cooling fluid,control devices for individual tubes at the rear thereof, each devicecomprising a tip of bendable thermostatic material and having petalscapable of closing together at low temperatures and opening outwardly athigher temperatures, the petals of adjacent control devices openingoutwardly for engagement with one another to limit the extent ofmovement at excessive temperatures.

JOHN E. WOODS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,189,786 Byrnes July 4, 19161,459,318 Birdsall June 19, 1923 1,864,052 Dykeman June 21, 19321,766,608 Crews June 24, 1930 FOREIGN PATENTS Number Country Date257,593 Great Britain Aug. 14, 1926 510,960 Germany Oct. 24, 1930Certificate of Correction Patent No. 2,437,287. March 9, 1948.

JOHN E. WOODS It is hereby certified that errors appear in the printedspecification of the above numbered patent requiring correction asfollows: Column 1, line 11, for the word liquid readflm'd; line 14,strike out will line 26, for Warm-jackets read warmup jackets; and thatthe said Letters Patent should be read with these corrections thereinthat the same may conform to the record of the case in thePatentvOffice.

Signed and sealed this 18th day of May, A. D. 1948.

.THOMAS F.- MURPHY,

Assistant Oomrntssz'oner of Patents.

